David Miliband, Peter Mandelson and Cathy Ashton thought to be on shortlist for diplomatic role

A decision on a new US ambassador is likely to be taken within days, with David Miliband, Peter Mandelson and Cathy Ashton all on the shortlist, the Guardian understands.

Whitehall sources said Downing Street is determined to press ahead with the appointment of a new US ambassador now that Donald Trump has been confirmed as the next US president.